1. Field of the Invention
The present invention relates to a device for obstructing the flow of lubricating oil leaking from the shaft-seal unit mounted on the drive shaft of a refrigerant compressor. More particularly, the present invention relates to a device for obstructing the flow of lubricating oil leaking from the shaft-seal unit on the drive shaft of a refrigerant compressor used for a climate control system of an automobile, so that an oil-dam is provided between the foremost end of the drive shaft and the shaft-seal unit mounted thereon, whereby lubricating oil which oozes out of the interior of the compressor body along the drive shaft is collected and diverted by an oil-dam, and is gradually drained away through a drain conduit formed in the body of the compressor.
2. Description of the Related Art
A refrigerant compressor, such as a swash plate type compressor or a wobble plate type compressor, used for compressing refrigerant gas in a climate control system of an automobile is provided with a drive shaft rotated by an automobile engine via a solenoid clutch unit so as to reciprocate pistons in cylinder bores of the cylinder block of the compressor. The drive shaft is rotatably held by the cylinder block and the compressor housing via anti-friction bearings, and the foremost end of the drive shaft is extended outward beyond the end of the housing so that it may be connected to the automobile engine. Therefore, a seal unit for making an oil-tight seal between the drive shaft and the housing is arranged adjacent to the anti-friction bearing held by the housing so that the interior of the compressor is isolated from the exterior of the compressor. Nevertheless, the interior of the body of the compressor is subjected to a high pressure during the operation of the compressor, and accordingly, lubricating oil suspended in the refrigerant gas is oozed out of the body through the shaft seal unit. The lubricating oil then flows toward the foremost end of the drive shaft along the surface thereof. As a result, a given part of the lubricating oil leaking through the seal unit of the drive shaft enters a solenoid clutch, i.e., a unit connecting the automobile engine and the drive shaft of the compressor, which is mounted on the foremost end of the drive shaft. In the solenoid clutch, the lubricating oil wets the faces of clutch plates and therefore, the clutch plates can slip and a power transmission from the automobile engine to the compressor is not properly performed.
Several measures have already been proposed, according to the prior art, to prevent the lubricating oil from leaking out of the compressor through the seal unit.
For example, Japanese Unexamined Utility Model Publication No. 50-110408 (JU-A-'408) discloses a prior art measure in which an oil absorbing member, made of oil absorbing material such as a felt material, is arranged adjacent to and in front of the shaft-seal unit in the axial bore of the housing of the compressor so as to absorb lubricating oil.
Another measure, in which a shaft seal member 61 is provided for sealing a drive shaft 68 extending through a central bore of a compressor housing 63, is shown in FIGS. 8 and 9. An oil blocking element 62, in the form of a bored disk having a curved edge, is press-fitted in the central bore 63a of the housing 63 so as to obstruct the flow of the leaking lubricating oil oozing through the shaft seal member 61. The lubricating oil obstructed by the oil block element 62 remains in an oil dam portion disposed between the oil block element 62 and the shaft seal member 61, and is gradually drained from the dam portion through a drain passageway 64 toward the exterior of the compressor. The oil blocking element 62 is made of a metallic plate 66 such as a steel plate coated with rubber material 5.
Nevertheless, the above-mentioned prior art measures have the defects described below.
The oil absorbing member of JU-A-'408 is insufficient in that it can absorb only a limited amount of the lubricating oil. Therefore, a certain amount of the lubricating oil cannot be absorbed by the oil absorbing member after the continuous use the oil absorbing member due to the fact that the oil absorbing member becomes impregnated with the lubricating oil after an extended operation of the compressor.
In the case of the oil blocking element 62 of the prior art, shown in FIGS. 8 and 9, the rubber portion 65 of the element 62 is elastically fitted in the central bore 63a of the housing 63 of the compressor. Therefore, it can be understood that when the oil blocking element 62 is manufactured, the rubber material 65 coating the metallic plate 66 is often broken at the stage where the peripheral portion of the metallic plate 66 is bent so as to form the curved periphery of the oil block element 62. This is because the rubber material 65 is excessively stretched during the bending process of the metallic plate 66.
On the other hand, when the rubber coating material 65 is applied to the metallic plate 66 after the bending of the periphery thereof, the coating process is very difficult and this increases the manufacturing cost of the oil blocking element 62.
Further, the bending of the metallic plate 66 must be done under precise dimensional control of the outer diameter of the oil blocking element 62 so that it may be accurately fitted and seated in the central bore 63a of the compressor housing 63. When the outer diameter of the oil blocking element 62 is larger than a predetermined dimension and outside the dimensional allowance, either the outer surface of the oil blocking element 62 or the bore surface of the housing 63 is damaged, and the rubber coating 65 may be removed from the metallic plate 66. When the outer diameter of the oil blocking element 62 is smaller than the predetermined dimension and outside the dimensional allowance thereof, the oil blocking element 62 is not sealingly fitted by press-fitting in the central bore 63a of the compressor housing 63, and accordingly, a leakage of oil cannot be completely prevented by the oil block element 62.